This non-analytic contribution \(\mathcal {C}^{(g)}_{0\ n.a.}\)  was earlier considered in
[1]}, [2]}. We observe that the coefficient of \({\rm log}(-s/m^2)\) , appearing in the last line of Eq.(REF ),
is different from Eq.(11) of [1]}, and Eq.(4.9) of [2]}:
in particular, the first term
proportional to \({\rm log}({\bar{\mu }}^2/(4E^2))\) 
is new; and the numerical factors of the last two terms, respectively proportional to \(E^3 m^2/s\)  and \(E^2m^2\) , are not the same.
More details on the source of the difference will be provided in Sec. REF .
